Reasons for low oxygen in the blood

Low oxygen levels in the blood are referred to as "hypoxaemia," a condition that can make you feel unusually sleepy and may even produce intermittent bouts of confusion. Low oxygen levels in your blood can also cause shortness of breath, headaches, fluid retention and insomnia. In some cases, low oxygen levels can be fatal when sleep apnoea or cardiac complications become a factor. For these reasons, the Mayo Clinic recommends notifying your doctor if you have a sudden onset of any of these symptoms.


Your metabolism produces carbon dioxide at a rapid pace and if your body does not go through the proper mechanics of breathing in oxygen and exhaling carbon dioxide, the oxygen levels in your blood can plummet as carbon dioxide levels rise. Hypoventilation can be the result of shallow breathing, breathing that is slow or abnormal lung functioning, according to Obesity can also be a factor in hypoventilation as well as deformity in the chest walls that affect the volume of air. Neurological disorders, such as anxiety, can also contribute to hypoventilation.

Ventilation Problems

Ventilation problems in the lungs can lead to low oxygen levels in the blood especially if the alveoli in the lungs are not functioning properly. Sometimes lung ventilation is disrupted when alveolar ventilation is not working in a pattern of uniformity. This lack of harmony causes a disruption in normal gas exchange and can be present even when the lungs are healthy. This pattern of alveolar insufficiency is sometimes referred to as "alveolar hypoventilation." The U.S. National Library of Medicine explains that alveolar ventilation problems are rare and the cause is unknown.

Decreased Diffusion Capacity

Diffusion capacity measures how smoothly air flows between the alveoli in the lungs and the capillaries, according to the International Association of Fire Fighters (IAFF). Oxygen levels in the blood are most affected by decreased diffusion capacity during exercise, but they may also be affected at high altitudes as well. This condition can be easily rectified with the assistance of respiratory therapy.


Normal levels of oxygen in the blood are highly dependent on healthy alveoli in the lungs, according to The University of Mississippi Medical Center. Blood that is shunted (re-routed) through the veins without coming in contact with the alveoli of the lungs will not be properly oxygenated. Shunting can result from stressors, such as pneumonia or pulmonary oedema or cardiac defects. The blood that enters the lungs from the heart is known as "mixed venous blood," which simply means that it has an equal mixture of carbon dioxide and oxygen. Shunting results in higher levels of carbon dioxide in the blood and subsequent low levels of oxygen.

The Oximeter

Low blood oxygen levels can be measured using a device known as an "oximeter." The oximeter probe is attached to the ear lobe or the finger of the patient. The probe sends out a light source absorbed by the haemoglobin in the blood. Sensors are able to detect the amount of oxygen in the haemoglobin through pulse rate and the amount of light absorption. An attached computer displays the patient's pulse rate and oxygen saturation, which should remain above 95 per cent. An oximeter does have some limitations, say experts at the World Federation of Societies of Anesthesiologists. For instance, bright lights can affect oxygen readings negatively as well as any nail polish that is on the fingernails. Also, an oximeter can only determine oxygen levels in the blood; carbon dioxide readings are impossible with such a device.

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About the Author

Jonae Fredericks started writing in 2007. She also has a background as a licensed cosmetologist and certified skin-care specialist. Jonae Fredericks is a certified paraeducator, presently working in the public education system.